As a consultant psychiatrist in the NHS I have spent 25 years treating the bravest and strongest people you could ever meet. They are battling through unimaginable suffering, sometimes deciding to continue living only because they do not want to hurt family and friends and tolerating the deficiencies of services and treatments.

During the past six months I have had the privilege of participating in the BBC documentary My Baby, Psychosis and Me with a group of women who have capped this bravery with an extraordinary and humbling altruism – by volunteering to share their experiences at the most vulnerable time in their lives.

The reality is that we are all vulnerable to mental illness. Our brains are the most complex structures in the universe and our minds are the uniquely individual products of that structure. It is not surprising then that occasionally things go wrong. The reasons things go wrong are much the same as in physical illness. There may be internal problems such as genetics (we probably all carry some genes for mental illness), infection or the effects of ageing. Most commonly damage comes from the outside.

Your brain is the most sensitive connection between you and the world, even better connected than your skin or your gut, and is designed to respond to even subtle things that happen around you. Traumatic experiences have an impact on your emotions, thoughts and behaviour. Research has shown that childhood is a time when our minds are particularly sensitive to what goes on around us in a way that can set the course for our adulthood. What science has been telling us more recently is that the earlier we go back in childhood, even into pregnancy, the greater the impact of our experiences on our later mental functioning.

For women with depression in pregnancy and postnatally, fear of what others will think is a major factor that stops them from revealing their suffering to anybody. This is causing a tragedy on an unbelievable scale: at least one in 10 women suffer from depression in pregnancy or postnatally, but only one in 10 of those women get the help they need. Even for extremely severe forms of illnesses, such as those depicted in the documentary, women in more than half of all areas in the UK do not have access to the specialist care they need during pregnancy and postnatally. If they are so ill that they need admission to hospital, the shortage of specialist mother and baby units means that many women are forcibly separated from their babies for weeks and sometimes months. The government and the NHS have said that services will be developed to end this inhumane treatment, but the fact that it has continued for so long goes to the very heart of our society’s neglect of people with mental illness. If this was the state of care for heart disease, the NHS would be abolished overnight.

The two women featured in the documentary, Hannah and Jenny, both suffered a severe episode of illness known as postpartum psychosis. To show what this illness is, and why specialist treatment should be available, they allow us to watch while they are extremely distressed, hallucinating, and suicidal.

As my patients, my overriding duty was towards their wellbeing. One of my legal responsibilities in relation to Hannah and Jenny’s decision to participate was to assess their capacity to consent to the filming. This involved deciding whether they understood the information relevant to the decision and were able to use that information to reach a decision. When filming started, Hannah and Jenny agreed to being filmed, even if they were not well enough to fully consider the question of broadcast. The BBC agreed not to use any of the footage until they had recovered, and assured the women and their families of their right to withdraw consent for use of any or all of the footage.

I knew that, despite the severity of postpartum psychosis, they would make a full recovery and so would gain full capacity to make their own decisions, with their families. In such circumstances it would have been patronising to make the decision on their behalf, and to deny them the opportunity to tell their story, unless I had evidence that the filming itself was harmful. The sensitivity and consideration of the producer/director and the cameraman ensured it was not. Once she had recovered, another woman who was originally filmed did choose to withdraw, but said she had no regrets about being filmed.

The women’s main concern was that they and their families might become the victims of stigmatising, discriminatory or cruel behaviour. But they also understood that raising awareness could reduce such behaviours towards them and their children. Patients frequently tell me that the benefits of being open about mental illness, particularly with family and friends, outweighs any disadvantages. Hannah and Jenny’s experience so far has been of overwhelming support, and even thanks, for what they have done. Both have told me that participating has helped them feel that some good would come of what was a terrible experience, and Hannah said that knowing this helped her at the time when she was most unwell.

When I was about to watch the documentary for the first time Rebecca Burrell, the producer/director, said: “I should warn you – it is very emotional.” I responded: “I’m sure, but I’m a psychiatrist, I see this every working day.”

I cried three times. The power of film to depict human experience seems to condense the emotional content in a way that touched me more than my daily work. Maybe it was being a passive observer, without the comfort and distraction of my therapeutic role, that moved me so much. Not that people working in mental health become immune to the suffering they see: every day I hear colleagues express how touched they have been by witnessing the pain of someone they were trying to help. We have the huge privilege of being able to do something about it and this is what keeps NHS professionals motivated to efforts that go well beyond the job description.

We also recognise that we are powerless to change some of the fundamental and pervasive challenges that people with mental illness face in our society. If this programme chips away at the stigma of mental illness, it will have been thanks to the strength and selflessness of two remarkable women.

• My Baby, Psychosis and Me is on BBC1 on Tuesday 16 February at 10.45pm and available on iPlayer after that. It is part of the BBC mental health season, In The Mind

• In the UK, the Samaritans can be contacted on 116 123. In the US, the National Suicide Prevention Hotline is 1-800-273-8255. In Australia, the crisis support service Lifeline is on 13 11 14. Hotlines in other countries can be found here